Laser scanner measurement system

ABSTRACT

The invention relates to a laser scanner measurement system, comprising a transmission unit consisting of a laser, beam deflection unit and transmitting optical system, and a receiving part with a photodetector which is arranged in the focal plane of the optical system destined for the receiving beam path. The invention is characterized in that the scanner unit and receiving unit are arranged on the same side in relation to the object and the surface normal of the receiving optical system is parallel to the direction of radiation of the scanner unit, i.e. that the scanner and receiver beam path in the outer area at all times have the same optical axis or that the axes are displaced parallel to each other and perpendicular to the direction ofmovement of the laser beam.

BACKGROUND OF THE INVENTION

The present invention relates to a laser scanner measuring system formeasuring objects accessible from one side and/or having complex shapesor structures, of the type which has an emitter unit that is providedwith a laser, a beam deflector unit and an optical emitter system whichdefine a scanning beam path as well as a scanning plane, as well as areceiving unit that includes a photo detector that is disposed in thefocal plane of an optical receiver system for a receiver beam path, thearrangement being such that the surface normal to the optical receiversystem is parallel with the scanning beam path.

PRIOR ART

For measuring bodies accessible from both sides, telecentric laserscanners have been used. FIG. 1 illustrates the principle of thesescanners. The scanner unit (1) emits a laser beam (2) directed onto theopposite receiver unit (4). When an object to be measured (3) is notplaced into the beam path the beam path will arrive in the receiverwithout being influenced, and is detected there with a photo diode (6)disposed in the focal point of the optical system of the receiver (5).When the beam hits an object to be measured, it is vignetted. Formeasuring, the laser beam is shifted in parallel with the lineinterconnecting the scanner and the receiver at a constant rate(scanning rate v_(s)). When the scanning rate is known it is possible tocalculate the size of the object to be measured along a direction normalon the shifting direction by derivation from the beam vignetting period.

The scanning rate can be taken into consideration according to thefollowing methods:

-   1. it is maintained constant, e.g. by means of an automatic    controller, and this constant value is considered as a parameter in    evaluation;-   2. it is measured. The measurement is performed, for example,    indirectly via a measurement of the angular speed of the deflector    unit in the scanner or directly by means of two photo diodes (7)    invariably arranged in the scanner. The photo diodes detect the time    of scan start (t_(start)) or of scan stop (t_(stop)). The scanning    rate is the quotient of the spacing of the photo diodes by the time    difference between the scan stop and the scan start. The spacing of    the photo diodes is determined by calibration.

In other scanning concepts, a specific diaphragm and two photo diodesare used, instead of one photo diode in the focal plane of the opticalreceiving system (EP 0 439 803). This concept permits the measurement ofthe shadow cast by objects having an extension smaller than the beamdiameter of the laser beam. To this end, the Fraunhofer diffractionpattern is analyzed when the laser beam is directed precisely onto theobject to be measured. This point of time is characterized by the factthat the sum of both intensities is at a maximum. The size of the objectto be measured is then determined by derivation from the ratio of theintensities measured by the individual photo diodes by that point oftime.

BRIEF SUMMARY OF THE INVENTION

In the last analysis, the laser scanners described above are onlysuitable for measuring objects accessible from both sides. On principle,all those properties can be measured which result in a completevignetting of the laser beam by the object to be measured. Suchproperties are, for instance:

-   -   the diameter in the case of solid rods,    -   the maximum extension along the scanning direction (the        direction in which the laser beam moves through the measuring        field in the course of time) in the case of profiled bodies,    -   the width of the teeth or the gaps between the teeth in the case        of comb-shaped structures.

Properties of an object, which do not result in complete vignetting orin Fraunhofer diffraction, respectively, or measuring objects accessiblefrom one side only cannot be measured by means of telecentric laserscanners in accordance with prior art.

The problem underlying the invention includes the improvement of thelaser scanner measuring system in such a way that it will be suitablefor measuring objects accessible from one side and/or having complexshapes or structures. In accordance with the invention, this is achievedby the laser scanner measuring system disclosed herein. Expedientembodiments of the measuring system are also disclosed herein.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is an example showing the known principle of a telecentric laserscanner;

FIGS. 2 a-d show examples of laser scanner measuring systems accordingto the present invention with different retro reflectors;

FIG. 3 shows an example of a laser scanner measuring system according tothe present invention including a dark stop;

FIG. 4 shows a further example of a laser scanner measuring systemaccording to the present invention including a dark stop;

FIG. 5 shows a further example of a laser scanner measuring systemaccording to the present invention including a dark stop;

FIG. 6 shows a further example of a laser scanner measuring systemaccording to the present invention including a dark stop;

FIG. 7 shows an example of a laser scanner measuring system according tothe present invention having several (additional) retro reflector unitson different positions relative to an object;

FIG. 8 shows an example of a laser scanner measuring system according tothe present invention, wherein the laser beam is split by optical meansin a direction orthogonal on the scanning plane and wherein a separatereceiver is provided for each scanning line;

FIGS. 9 a/b show two examples wherein a laser scanner measuring systemaccording to the present invention is built as a modular system;

FIGS. 10 a/b show different elements for use in a modular systemaccording to FIGS. 9 a/b; and

FIG. 11 schematically shows a laser scanning measurement system forcontrolling a production process.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of the invention is a laser scanner measuring systemfor measuring objects accessible from one side and/or having complexshapes or structures. In the following description, common referencenumerals described herein also refer to similarly numbered featuresthroughout the drawings.

The measurement from one side is achieved by a laser scanner measuringsystem which includes, for instance, a combined illuminating/receivingunit (cf. item 8 in FIG. 2). The laser beam, which is emitted from thelaser 12, passes through the beam splitter 11 and arrives, via thedeflector unit 10 and the combined optical emitter/receiving unit 13, inthe outside space. When the laser beam hits on a reflecting surfaceelement of the object to be measured, which has a surface normalcoinciding with the direction of the laser beam, the laser beam isreflected back into the receiver unit. It arrives, via the opticalsystem, the deflector unit and the beam splitter, on the detector 6. Itis then possible to derive the position of this surface element with anorientation orthogonal on the laser beam from the measurement of thepoint of time by which the laser beam is reflected back. In this mannerit is possible, for example, to determine the center of a polished orglossy rod having a circular cross-section.

The extension of objects having a dull surface can be measured if thescattering properties of the object surface can be distinctlydistinguished from the scattering characteristics of the background 9.

When the laser beam scans over an object surface having scatteringproperties varying in the measuring field, the extension of zones havinga distinctly different scattering characteristic can be measured. Whenthe object has a dull surface in the solid state and a glossy surface inthe liquid state, for instance, it is possible to determine the size ofthe liquid zone from the development of intensity versus time.

The measurement of the beginning or the end of a scan can be achieved byproviding two retro-reflecting markers (sheet points) which are arrangedin the scanner receiving unit. The points of time can then be detectedby means of the receiving diode.

When a retro-reflecting unit can be arranged behind the object to bemeasured, when seen in the direction of emission (e.g. aretro-reflecting sheet 9 a, mirrored cuboid corner 9 b or a “lens-type”retro reflector), it is possible to measure further properties of theobject. The retro reflector unit reflects the impinging beams alongtheir own extension or in the direction orthogonal on the scanning plane(defined by the optical axis of the laser scanner and the direction ofmovement of the laser beam) back into the scanner receiving unit with anoffset. With special configurations or arrangements of the retroreflector, specific types of measurement can be implemented. Thefollowing particularly excellent embodiments should be mentioned here asexamples:

-   -   when the sheet reflector (9 b in FIG. 2 b) is used it is        possible to determine the cast shade and to derive from the        shade the outside contour of an object to be measured, which is        practically accessible from one side only;    -   other retro reflectors (in the form of two mirrors orthogonal on        each other (cf. 9 c in FIG. 2 c), prisms or retro reflectors        consisting of a combination of two spherical lenses or        cylindrical lenses, respectively, which is made reflective on        the rear side (9 d in FIG. 2 d)) permit the measurement of the        maximum or mean extension of the object to be measured via the        direction orthogonal in the axis of symmetry of the retro        reflector, depending on the dimensioning of the optical and        electronic systems of the scanner system.

Apart from the possibility to detect further geometric parameters of theobject to be measured or the possibility to measure objects accessiblewith difficulties only, an inventive array with retro reflectors offersthe advantage that only one unit must be cabled. When a sheet reflectoris used it is moreover not required to adjust the reflector unit.

A very precise determination of the point of time by which the laserbeam hits the object to be measured can be implemented by arranging adark stop ahead of the photo detector and by letting the electronicanalysing system determine the points of time at which the radiationincident on the detector reaches a maximum level.

This technique of evaluation makes use of the diffraction of thelimiting rays on the object edges. It is only slightly influenced byvariations of the laser output and a variation of the intensity of thelaser radiation in the course of the scanning operation. It can berealised with both a laser scanner with separate emitter and receiverunits (cf. FIG. 4) and laser scanners comprising a jointemitter/receiver unit (cf. FIG. 3). In the latter case, it may beexpedient to dispose an additional lens 16 ahead of the dark field stop.

When telecentric laser scanners in correspondence with prior art areused to measure glass tubes, malfunctioning may occur because there arethree additional excellent beam paths, apart from the shade edges on theoutside diameter, along which light arrives from the scanner unit in thereceiver:

-   1. tube centre: the tube produces the effect of a lens there, the    central beam arrives on the detector practically without any    weakening;-   2. two reflections on the inner wall: the radiation incident on the    tube is refracted, when entering the tube, towards the centre of the    tube, is reflected on the inner wall and undergoes further    refraction when leaving the tube. The incident and emerging beams    are parallel to each other at precisely two locations on the tube so    that the beams can be detected in the receiver. The positions of    these locations on the tube is dependent on the diameter, the    thickness of the wall and the refractive index of the tube.

The amplitudes of these signals are low in arrays in correspondence withprior art and yet they are suitable to interfere with measurement. Oneof the inventive arrays leads to the effect that the reflections on theinner wall provide very well detectable signals with a highsignal-to-noise ratio from which the wall thickness of the tubes can becalculated. These signals are appropriate for very good analysis bydetermining those points of time by means of the electronic analyzingsystem by which the signal reaches local maximum levels. One method tothis end consists in a verification of the following conditions by meansof the electronic analyzing system 21:

-   1. The derivative of the signal presents a zero crossing;-   2. The signal exceeds the noise.

When the times by which both conditions are satisfied are measured thediameter and two values of the wall thickness can be detected on glasstubes in a manner comparatively insensitive to interference.

Interference may occur with this type of evaluation of the edges and thereflection when the measurement must be performed in a dust-loadedenvironment or in an environment presenting strong movements orturbulences of the air. In these cases a system can be employed toachieve a substantial increase of the robustness of the measurement. Tothis end, the receiver beam path is split by means of a beam splitter 17(cf. FIG. 5 and FIG. 6) in such a way that one part of the radiationarrives on a photo diode with a dark field stop ahead of it, whileanother part of the radiation arrives directly on a second photo diode.The edges can be detected in the aforedescribed manner. The intensitymeasurement, which is additionally provided, issued to ensure that onlysignal maximums in the zone between the shadow edges will be used forevaluation. Interference caused by striation in the air or by dust inthe zone outside the shadow edges are eliminated by inhibiting theevaluation as long or as soon as the signal on the second photo diodeexceeds a threshold (which can be set if necessary).

An equivalent detection of the edge and reflection positions can beperformed when, a photo diode array or a photo diode matrix is arranged,instead of one photo diode, in the focal plane of the optical system ofthe receiver or behind the beam deflector unit. It must be so disposedthat one element of the array detects that fraction of the radiationwhich passes through the outside space without any interaction with theobject to be measured. The signal of this element displays a developmentversus time which can also be detected with the second photo diode, butit has the double amplitude (since losses are not created on the beamsplitter).

When a position-sensitive photo diode is provided it is possible tomeasure the position of the shadow edges or of the inside reflections,and additionally the mean differential angle of the surfaces of apartially transparent object to be measured, relative to the scanningdirection and the scanning plane. The additional measurement makes useof the effect that the angle of the surface elements entails adeflection of the transmitted beam, which can be detected as leveloffset in the focal plane.

A position-sensitive photo diode moreover permits the simultaneousdetection of the reflection on the object surface and of the tiltingangle of the object relative to the scanning plane. To this end, it isincorporated as a sensor in a receiver which is arranged at an angledifferent from 0° or 180° relative to the optical axis of the scanner.

When two receivers are arranged on opposite sides of the object to bemeasured, at an angle relative to the scanning direction, it is possibleto measure objects to be measured which have an extension wider than thewidth of the scanned zone. When the receivers are arranged, forinstance, at angle of ±90° relative to the beam direction, a reductionby a factor of 2⁰⁵ is achieved for objects having a circularcross-section. This means that objects having an extension of up to 1.4times that of the scanned zone can still be measured.

The arrangement of several (additional) retro reflector units onappropriate locations constitutes an equivalent, provided that acombined emitter/receiver unit is used (cf. FIG. 7).

The angle of the receiver or the retro reflector unit(s) relative to thescanning direction can be selected so as to vary the scale of reductionover a wide range.

When several retro reflectors are used for measurement and arranged, forexample, at angles of 180°, +90° and −90° relative to the scanner unitthe centre and several points along the periphery of the object to bemeasured are obtained (cf. FIG. 7). On the basis of these values it ispossible, for instance, to measure the variation of the shape of theobject to be measured from the ideal shape. The measured objectcross-section can be defined, for instance, by an ellipse. The variationof the cross-section from an ideal circular shape can then be determinedfrom the parameters of the ellipse.

When such an array is arranged with a scanner having a convergent ordivergent emitting direction two tangents on the object to be measuredcan be determined from the limiting rays (shadow edges). Additionalpoints on the object surface are obtained by an evaluation of the retroreflected beams. It is possible to determine the diameter and theposition of the object to be measured in the scanning plane from thesemeasured parameters.

This arrangement entails further advantages when transparent tubes aremeasured. The distance between the rays reflected on the outside walland the inside wall is substantially greater with this array than in the180° array. It allows therefore for an improvement of the measuringprecision or the measurement of thin-walled tubes, respectively.

As shown in FIG. 8, further geometric characteristics of the object tobe measured are accessible to measurement if the laser beam is split byoptical means 18 (such as a grid disposed in parallel with the scanningdirection) in a direction orthogonal on the scanning plane. Whenseparate receivers 4 are used, a separate receiver is provided for eachscanning line. When a combined scanner/receiver unit is used, a grid isarranged preferably ahead of the beam splitter for splitting between thepaths of the emitted and received beams, and splitting is performed bymeans of the grid. Then one respective photo diode or an element of aphoto diode array is disposed in the path of the received beam in thefocal point of the optical system per beam path to be evaluated. Due tothe splitting of the scanning beam path into several partial beam paths,it is possible to determine the development of the object geometry alongthe plane orthogonal to the scanning plane. With this provision, it ispossible, for instance, to detect reliably a conical extension of theobject contour or a curvature of the object to be measured.

A wider angle between the partial beam paths can be achieved, ifnecessary, by the application of an optical cylinder system in theemission beam path.

An extension of the measuring method becomes possible by an opticalstructural element for splitting a laser beam into several partial beampaths located in the scanning plane for instance a grid having linesextending orthogonally on the scanning plane).

When the element is disposed in the zone between the laser and the focalpoint of the optical scanner system several beams hit the deflector unitin the focal plane of the optical emitter system. As a result, thescanner unit emits several beam bundles. They are located in thescanning plane (the plane defined by the scanning direction and theoptical axis) but they present angle relative to the scanning direction(which may possibly vary as a function of the site). These beams arevignetted, diffracted or reflected on the measured object. To this endthere one photo detector or an element of a detector array must beprovided there per partial beam path. It is then possible to measure theposition of the object in the illuminated plane via an analysis of theshadow edges or the reflection or diffraction peaks, respectively, ofthe corresponding development of intensity versus time.

The arrangement of polarising beam splitters in the beam path permitsthe detection of the polarisation state of the detected radiation. Inthis way, those object properties can be measured which take differentinfluences on the polarisation states of the transmitted beams. Onerespective additional detector element must be provided per measurand tobe detected, in addition to the beam splitter. The object characteristicto be detected can be determined from the differences between theintensities.

For birefringent or optically active sheets it is possible, forinstance, to determine the length of the optical path and thus thethickness of the layer or the ability of rotation towards the opticalaxis. To this end a scanner with a circularly polarised laser beam isused, together with a polarising beam splitter in the emitter orreceiver beam path, and for each partial beam path a photo detector(element) is disposed.

Further additional parameters of the object can be measured, which takean influence on the polarisation of the transmitted radiation, providedthat the radiation components of different polarisations are split bothin the emitter and the receiver beam paths.

When, in addition to this splitting, one or several filters 20 areinserted into the receiver beam path, which are selective in terms ofwavelength, it is possible to measure the following parameters forsubstances (such as PET) displaying an intrinsic polarised fluorescence:

-   1. position of the object and extension in the scanning direction,-   2. development of the 1^(st) momentum of the orientation    distribution function,-   3. development of the 2^(nd) momentum of the orientation    distribution function.

In the case of PET, the intrinsic polarised fluorescence occursselectively in the non-crystalline zones. These are decisive for themechanical properties and for the receptivity for dyes of the object.Via a measurement of the momentums of the orientation distributionfunction, it is possible to use the aforedescribed system for aselective detection of the development and gradient of these parametersin the material.

Further characteristic parameters of the object to be measured can bedetected if two beam paths (the beam path coming from the object and a(possibly modulated) reference beam path or a second beam path passingthrough the object space or coming from the object) are superimposed inthe receiver unit in such a way that the beams will interfere with eachother. Depending on the configuration of this beam path and the signalanalysis it is then possible, in addition to the detection of theaforedescribed characteristic parameters, to detect the spacing or thecontour of an object to be measured along the direction of the opticalaxis, or to detect the velocity of the movement of the object to bemeasured through the scanning plane. When the retro reflector principleis applied it is possible to establish the reference beam path in theform of a Michelson interferometer, for instance, inside the combinedemitter/receiver unit. In the event of application of a separatereceiver unit, the reference beam path (passing by the object to bemeasured) can be guided through the object space or by means of opticalguides from the scanner to the receiver.

The aforementioned types of measurement may be combined with each otheroptionally. This can be realized in a particularly expedient manner whena modular system is provided which includes a scanner head, a measuringmodule and possibly a receiver housing with the optical system. As shownin FIG. 9, the scanner unit 1 includes a laser (12), a deflector unit(10), and an optical system 19, as wells as the following additionalcomponents, if necessary (when the reflection or retro scattering ismeasured or when a retro reflector unit is employed): receiver module(20) and scan start and scan stop reflector (14).

The receiver module is provided with means for mounting detector modulesthereon (cf. the schematic illustration in FIG. 10 b), lenses or mirrors(items A to H in FIG. 10 a) and beam splitters (cf. items St1 to St3 inFIG. 10 a). Alternatively, a position-resolving photo diode D5 can beused in the present invention. Depending on the equipment of thereceiver module and the selected arrangement various measured parameterscan be derived. Some examples thereof are listed in Table 1:

TABLE 1 Examples of different configurations of an inventive laserscanner measuring system Mode Receiver Object Parameters Element Item 1separate glass tube diameter, photo diode array D2 A 180° wallthickness, position of centre 2 combined glass tube diameter, beamsplitter 50% St1 wall thickness, photo diode array D2 C position ofcentre 3 separate transparent position beam splitter polarising St1 180°fibres diameter, annular photo diode D4 B degree of polarisation photodiode D1 C 4 combined transparent position beam splitter 50% St1 fibresdiameter, beam splitter polarising St2 degree of polarisation annularphoto diode D4 B photo diode D1 C 5 combined optically extension, beamsplitter 50% St1 active layers thickness of layer beam splitterpolarising St2 photo diode array D2 B photo diode 1 C 6 combined rods,tubes diameter, grid parallel to conicality, scanning direction Hdeflection lens B beam splitter 50% St1 lens B beam splitter 50% St2photo diode array D2 D photo diode array D3 E 7 combined rods, tubesdiameter, two-axis grid H position in the beam splitter St3 scanningplane, lens C conicality, beam splitter 50% St1 deflection, lens Cvelocity beam splitter 50% St2 photo diode array D2 D photo diode arrayD3 E photo diode D1 F (active) mirror G

The laser scanners according to the present invention are particularlysuited for application for controlling manufacturing processes as theydetect relevant process parameters which are then supplied as inputsignals to a process controller or automatic control system.

1. A laser scanner measuring system for measuring macroscopic geometricparameters of an object, the macroscopic geometric parameters includingat least one of contour, size and wall thickness of the object, thesystem comprising: an emitter unit having a laser, a beam deflector unitand an optical emitter system which define a scanning beam path and ascanning plane of a scanning beam emitted from said emitter unit; areceiver unit including a photo detector disposed in the focal plane ofan optical receiver system in a path of a receiver beam, wherein thesurface normal of said optical receiver system is parallel with thescanning beam path, the receiver unit receiving said receiver beam afterscanning the object and generating a signal; a dark field stop disposedahead of said photo detector in the receiver beam path in the focalplane of said optical receiver system where the dark field stop isarranged to block a central beam in the receiver beam path; a beamsplitter ahead of said dark field stop for splitting a partial beam fromthe receiver beam path, said photo detector including a photo diodearranged in said partial beam, said photo diode being disposedapproximately in the focal point of said optical receiver system; and anelectronic analyzing system for determining the macroscopic geometricparameters from the signal.
 2. A laser scanner measuring systemaccording to claim 1, wherein said emitter unit and said receiver unitare disposed on the same side relative to the object to be measured. 3.A laser scanner measuring system according to claim 2, furthercomprising a retro reflector unit arranged behind said object to bemeasured, when seen from said emitter unit, which retro reflector unitreflects any incident radiation back either in itself or with a paralleloffset such that the receiver beam path will be located in a planeoffset in parallel from the scanning plane.
 4. A laser scanner measuringsystem according to claim 1, further comprising at least one retroreflector or a retro-reflecting marker disposed inside said emitterunit.
 5. A laser scanner measuring system according to claim 1, furthercomprising additional receiver units or retro reflectors disposed at anangle different from 0° or 180° relative to an optical axis of theemitter unit in the scanning plane.
 6. A laser scanner measuring systemaccording to claim 1, further comprising an optical system arranged inthe scanning beam path for splitting the scanning beam in a directionorthogonal on a scanning direction.
 7. A laser scanner measuring systemaccording to claim 6, wherein there is formed a grid having linesoriented orthogonally with respect to the scanning direction.
 8. A laserscanner measuring system according to claim 1, further comprising anoptical system arranged in the scanning beam path for splitting thescanning beam in a direction parallel with a scanning direction.
 9. Alaser scanner measuring system according to claim 8, where there isformed a grid having lines oriented parallel with respect to thescanning direction.
 10. A laser scanner measuring system according toclaim 1, further comprising optical elements disposed in the scanningbeam path and/or the receiver beam path for radiation of differentpolarisation.
 11. A laser scanner measuring system according to claim 1,further comprising filters selective in terms of wavelength disposed inthe receiver beam path.
 12. A laser scanner measuring system accordingto claim 11, wherein said filters are interference filters, colorfilters or cut-off filters.
 13. A laser scanner measuring systemaccording to claim 1, wherein said emitter unit and said receiver unitform a single combination unit and wherein a reference beam path isrealised in the combination unit, outside the combination unit or bymeans of a light guide, which is superimposed by the receiver beam pathcoming from the object to be measured in such a way that a resultinginterference pattern which varies locally and in the course of time isdetected by means the photo detector.
 14. A laser scanner measuringsystem according to claim 1, wherein said measuring system is adapted tocontrol a production process.
 15. A laser scanner measuring systemaccording to claim 1, wherein said electronic analyzing system isadapted to determine diameters in two orthogonal directions of atransparent rod or tube placed as said object in the scanning beam pathfrom intensity maxima on the photo detector.
 16. A laser scannermeasuring system according to claim 1, wherein said electronic analyzingsystem is adapted to determine a diameter and wall thickness of atransparent tube placed as said object in the scanning beam path fromintensity maxima on the photo detector.
 17. A laser scanner measuringsystem for measuring macroscopic geometric parameters of an object, themacroscopic geometric parameters including at least one of contour, sizeand wall thickness of the object, the system comprising a scanner unitformed by an emitter unit having a laser, a beam deflector unit and anoptical emitter system, which define a scanning beam path as well as ascanning plane of a scanning beam emitted from said emitter unit; areceiver unit including a photo detector disposed in the focal plane ofan optical receiver system in a path of a receiver beam, the surfacenormal of said optical receiver system being parallel with the scanningbeam path, and said photo detector being a photo diode array containingat least two photo diodes or a position-resolving photo diode, thereceiver unit receiving said receiver beam after scanning the object andgenerating a signal; and an electronic analyzing system for determiningthe macroscopic geometric parameters from the signal.
 18. A laserscanner measuring system according to claim 17, wherein said emitterunit and said receiver unit are disposed on the same side relative tothe object to be measured.
 19. A laser scanner measuring systemaccording to claim 18, further comprising a retro reflector unitprovided behind said object to be measured, when seen from said emitterunit, which reflects any incident radiation back either in itself orwith a parallel offset such that the receiver beam path will be locatedin a plane offset in parallel from the scanning plane.
 20. A laserscanner measuring system according to claim 17, further comprising atleast one retro reflector or a retro-reflecting marker disposed insidesaid emitter unit.
 21. A laser scanner measuring system according toclaim 17, further comprising additional receiver units or retroreflectors disposed at an angle different from 0° or 180° relative to anoptical axis of the scanner unit in the scanning plane.
 22. A laserscanner measuring system according to claim 17, further comprising anoptical system arranged in the scanning beam path for splitting thescanning beam in a direction orthogonal on a scanning direction.
 23. Alaser scanner measuring system according to claim 22, wherein there isformed a grid having lines oriented orthogonally with respect to thescanning direction.
 24. A laser scanner measuring system according toclaim 17, further comprising an optical system arranged in the scanningbeam path for splitting the scanning beam in a direction parallel withthe scanning direction.
 25. A laser scanning measuring system accordingto claim 24, where there is formed a grid having lines oriented parallelwith respect to the scanning direction.
 26. A laser scanner measuringsystem according to claim 17, wherein said electronic analyzing systemis adapted to determine diameters in two orthogonal directions of atransparent rod or tube placed as said object in the scanning beam pathfrom positions of local intensity maxima on one photo diode of the photodiode array or the position resolving photo diode.
 27. A laser scannermeasuring system according to claim 17, wherein said electronicanalyzing system is adapted to determine a diameter and wall thicknessof a transparent tube placed as said object in the scanning beam pathfrom positions of local intensity maxima on one photo diode of the photodiode array or the position resolving photo diode.